JP4036060B2 - Electronic camera and white balance control circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic camera capable of flash photography (strobe photography) and a white balance control circuit applied to the electronic camera.
[0002]
[Prior art]
In general, white balance control in an electronic camera is performed based on the color temperature of illumination and the type of illumination obtained from a photographed image, the output of a colorimetric sensor, or the like. Note that the reason why the illumination is based on the type of illumination is that the two different types of illumination (for example, fluorescent light and natural light) have different white balance control values even if they have the same color temperature.
[0003]
On the other hand, during flash photography, the illumination is a combination of flash (strobe light) and external light (non-flash illumination), so the ideal white balance control is the type of external light, the color temperature of the external light, the flash And the color temperature of the flash.
However, since the type of flash and the color temperature of the flash are actually specific to the flash light emitting device to be used, the following (1) to (4) are currently proposed as methods for determining the white balance control value. And so on.
[0004]
(1) The white balance control value is fixed to the optimum value for the illumination of the flash alone, assuming that the influence of the flash on the subject is overwhelmingly stronger than any external light.
(2) The type of external light and the color temperature of the external light are obtained based on the preliminary photographing before the flash emission or the output of the colorimetric sensor, and the optimal value for such external light and the optimal value for the illumination of the flash alone And the white balance control value is set to the average value.
[0005]
(3) In (2), the brightness of the external environment is further measured to predict the flash emission amount (that is, the degree of influence of the flash on the subject), and the average is set to a weighted average corresponding to the degree of influence.
(4) The type of external light and the color temperature of external light are obtained based on preliminary shooting before flash emission or the output of a colorimetric sensor, and the distance of the subject is measured to predict the amount of flash reaching the subject. The optimal value for the external light and the optimal value for the illumination of the flash alone are selected in accordance with the amount of the arrival (in addition, the distance measurement, the prediction of the amount of arrival, and the selection of the optimum value are selected by the outside world). For each of the areas.)
[0006]
[Problems to be solved by the invention]
However, according to the method (1), since white balance control is always performed with the same white balance control value, a specific flash photography scene is reproduced extremely inappropriately. For example, a flash photography scene where the background of the subject is far away and the flash does not reach the background and the background lighting color temperature is low is reproduced with an unnatural reddish background. Sometimes.
[0007]
On the other hand, when any one of the methods (2), (3), and (4) is adopted, although there is a possibility that it can cope with various flash photography scenes, the degree of satisfaction of the user with respect to the reproduced image although the processing is complicated Is not so expensive.
Therefore, according to the present invention, the white balance control value at the time of flash photography can be appropriately set by a relatively simple process (specifically, the process is simpler than the methods (2), (3), and (4)). An object of the present invention is to provide an electronic camera and a white balance control circuit that can be set more appropriately than the method (1).
[0008]
[Means for Solving the Problems]
The electronic camera according to claim 1 is an electronic camera having a flash light emitting device or a connection terminal to the flash light emitting device, an image pickup means for picking up an image of the outside world and acquiring image data, and flash light emission by the flash light emitting device. Based on the image data acquired during, the color temperature calculation means for calculating the color temperature of the overlapping illumination by external light and flash, and the image data according to the calculated color temperature which is the calculated color temperature White balance control value determining means for determining a white balance control value for the white balance control value, and when the calculated color temperature falls within a predetermined range, the white balance control value determining means reflects the calculated color temperature on the white balance control value. It is characterized by reducing.
[0009]
The electronic camera according to claim 2 is the electronic camera according to claim 1, wherein when the calculated color temperature is higher than a color temperature of illumination of the flash alone, the white balance control value determining unit determines the white balance control. It is characterized in that the value is close to the optimum value for the illumination.
The electronic camera according to claim 3 is the electronic camera according to claim 2, wherein the white balance control value determining means is configured to control the white balance when the calculated color temperature is higher than a color temperature of the flash only illumination. The value is matched to the optimum value for the illumination.
[0010]
The electronic camera according to claim 4 is the electronic camera according to any one of claims 1 to 3, wherein the white balance control value determining means is configured to calculate the illumination color equivalent to daylight. When the temperature is lower than the color temperature, the white balance control value is brought close to an optimum value for the illumination of the flash alone.
The electronic camera according to claim 5 is the electronic camera according to claim 4, wherein the white balance control value determining means is such that the calculated color temperature is lower than a color temperature of illumination equivalent to daylight and equivalent to sunset light. When the color temperature is lower than the illumination color temperature, the white balance control value is made closer to the optimum value.
[0011]
The electronic camera according to claim 6 is the electronic camera according to claim 5, wherein the white balance control value determining means has the calculated color temperature lower than a color temperature of illumination equivalent to daylight and equivalent to sunset light. When the color temperature is lower than the illumination color temperature, the white balance control value is made to coincide with the optimum value.
The electronic camera according to claim 7 is the electronic camera according to any one of claims 1 to 3, wherein the white balance control value determining means is configured to calculate the illumination color equivalent to daylight. When the temperature is lower than the color temperature, the white balance control value is brought close to an optimum value for the illumination.
[0012]
An electronic camera according to an eighth aspect of the present invention is the electronic camera according to the first aspect, further comprising means for identifying the type of the external light during non-emission of the flashlight, wherein the white balance control value determining means is The relationship between the calculated color temperature range and the reflection amount is varied according to the identified type.
The white balance control circuit according to claim 9 is a white balance control circuit applied to an electronic camera capable of flash photography, and is based on image data acquired by flash photography by the electronic camera and external light and flash light. And a color temperature calculation means for calculating a color temperature of the overlapping illumination, and a white balance control value determination means for determining a white balance control value for the image data in accordance with the calculated color temperature which is the calculated color temperature. The white balance control value determination means reduces the amount of reflection of the calculated color temperature with respect to the white balance control value when the calculated color temperature falls within a predetermined range.
[0013]
The white balance control circuit according to claim 10 is the white balance control circuit according to claim 9, wherein when the calculated color temperature is higher than a color temperature of illumination of the flash alone, The white balance control value is brought close to an optimum value for the illumination.
A white balance control circuit according to an eleventh aspect is the white balance control circuit according to the tenth aspect, wherein the white balance control value determining means is configured such that when the calculated color temperature is higher than a color temperature of illumination of the flash alone. The white balance control value is matched with an optimum value for the illumination.
[0014]
The white balance control circuit according to claim 12 is the white balance control circuit according to any one of claims 9 to 11, wherein the white balance control value determining means is configured such that the calculated color temperature is daylight. When the color temperature is considerably lower than the color temperature, the white balance control value is brought close to the optimum value for the illumination of the flash alone.
[0015]
The white balance control circuit according to claim 13 is the white balance control circuit according to claim 12, wherein the white balance control value determining means has the calculated color temperature lower than the color temperature of illumination equivalent to daylight, In addition, when the color temperature of the illumination equivalent to the sunset light is lower, the white balance control value is further brought closer to the optimum value.
[0016]
The white balance control circuit according to claim 14 is the white balance control circuit according to claim 13, wherein the white balance control value determining means has the calculated color temperature lower than the color temperature of illumination equivalent to daylight, In addition, when the color temperature of the illumination equivalent to the sunset light is lower, the white balance control value is made to coincide with the optimum value.
[0017]
The white balance control circuit according to claim 15 is the electronic camera according to any one of claims 9 to 11, wherein the white balance control value determining means is configured such that the calculated color temperature corresponds to daylight. When the color temperature is lower than the color temperature of the illumination, the white balance control value is brought close to the optimum value for the illumination.
The white balance control circuit according to claim 16 is the white balance control circuit according to claim 9, wherein the electronic camera is an electronic camera capable of identifying the type of the external light, and the white balance control circuit The value determining means varies the relationship between the calculated color temperature range and the reflection amount according to the identified type.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. 1, 2, 3, 4, and 5.
[0019]
In the present embodiment, a camera system to which the electronic camera of the present invention (the white balance control circuit of the present invention is mounted) will be described.
FIG. 1 is a schematic configuration diagram of a camera system according to the present embodiment.
The camera system includes an electronic camera body 11, a photographing lens 12, and an electronic flash device 13. For example, the photographing lens 12 and the electronic flash device 13 can be attached to and detached from the electronic camera body 11.
[0020]
The electronic camera body 11 is provided with an operation button 16 such as a release button, and the operator can switch the state of the electronic camera body 11 between the non-flash photography mode / flash photography mode and the like via the operation button 16. A photographing instruction can be given to the electronic camera body 11 at a desired timing.
Incidentally, the electronic camera body 11 is, for example, a single-lens reflex camera as shown in FIG. 1 (in addition to the shutter 11e and the CCD image sensor 11f, it includes a mirror 11a, a screen 11b, a pentaprism 11c, an eyepiece 11d, and the like. ).
[0021]
A dotted line in the electronic camera body 11 indicates a colorimetric sensor 11h used in a second embodiment to be described later, and a condensing lens that condenses the incident light beam to the colorimetric sensor 11h (first). In the embodiment, the colorimetric sensor 11h and the condenser lens 11g are not used because they are not used.)
At the time of non-photographing, the mirror 11a is in the “mirror down state” as indicated by the dotted line, and the light flux from the object field incident from the photographing lens 12 is operated via the mirror 11a, the screen 11b, the pentaprism 11c, and the eyepiece 11d. Led to the eyes of the person. In this state, the operator can visually observe the object scene. In this state, the color of the object scene can be measured by the colorimetric sensor 11h.
[0022]
At the time of shooting, the mirror 11a in the electronic camera body 11 is in the “mirror up state” as shown by the solid line, and the shutter 11e is driven, and the CCD image pickup device 11f is exposed by the light flux from the object scene. In this state, when the CCD image sensor 11f is driven, an image of the object scene is acquired.
On the other hand, the electronic flash device 13 is electrically connected to the electronic camera body 11 through a contact (not shown), and is driven according to an instruction from the electronic camera body 11 by an electric signal.
[0023]
At the time of shooting, particularly when the electronic camera body 11 is set to the flash photography mode, the electronic camera body 11 flashes the electronic flash device 13 so that the object scene is illuminated at the exposure timing described above. Instructions are given.
When the flash amount of the electronic flash device 13 is variable, an instruction is given from the electronic camera body 11 to the electronic flash device 13 for the flash amount.
[0024]
FIG. 2 is a block diagram of the circuit unit 15 provided in the electronic camera body 11. The operation of the electronic camera body 11 described above is such that the CPU 15a of the circuit unit 15 drives each part (CCD image sensor 11f, shutter 11e, mirror 11a, etc.) in the electronic camera body 11 in accordance with the operation of the operation button 16. This is achieved as a result of the control.
[0025]
In addition to the CPU 15a, the circuit unit 15 includes a signal processing circuit 15b, a white balance control circuit 15c, a color conversion circuit 15d, a gradation conversion circuit 15e, an image memory 15f, and the like. The signal processing circuit 15b, white balance control circuit 15c, color conversion circuit 15d, gradation conversion circuit 15e, and image memory 15f are controlled by the CPU 15a.
[0026]
The circuit unit 15 receives an image signal acquired by the CCD image sensor 11f. This signal is subjected to predetermined signal processing in the signal processing circuit 15b, white balance processing in the white balance control circuit 15c, color conversion processing in the color conversion circuit 15d, and gradation conversion processing in the gradation conversion circuit 15e. Stored in the image memory 15f.
[0027]
The white balance control circuit 15c includes, for example, a white balance processing unit 15c-1, a color temperature calculation unit 15c-2, and a white balance gain determination unit 15c-3.
The white balance processing unit 15c-1 multiplies the R component and B component (R, B) of the signal (R, G, B) output from the signal processing circuit 15b by a white balance gain (Kr, Kb). Thus, white balance processing is performed.
[0028]
The white balance gain (Kr, Kb) is determined for each shooting (that is, for each image).
The determination is made by the color temperature calculation unit 15c-2 and the white balance gain determination unit 15c-3.
The color temperature calculation unit 15c-2 refers to the signal for one image output from the signal processing circuit 15b, and calculates the color temperature of the illumination of the object scene by any known method based on the signal.
[0029]
The white balance gain determination unit 15c-3 determines the optimum white balance gain (Kr, Kb) for the image according to the color temperature output from the color temperature calculation unit 15c-2 (hereinafter referred to as “calculated color temperature”). ).
In order to simplify the determination process, the white balance gain determination unit 15c-3 includes, for example, a lookup table (see the lower right table in FIG. 2).
[0030]
In the lookup table, each value of the color temperature and the optimum white balance gain (Kr, Kb) for each color temperature are stored in association with each other.
In the present embodiment, the calculated color temperature output from the color temperature calculation unit 15c-2 and the color temperature input to the lookup table when referring to the lookup table are not necessarily the same. , Referred to as “reference color temperature”.
[0031]
Here, at the time of non-flash photography, since only the outside light illuminates the object scene, the calculated color temperature output from the color temperature calculation unit 15c-2 indicates the color temperature of the outside light. On the other hand, at the time of flash photography, since it is the overlapping illumination of the external light and the flash that illuminates the object scene, the calculated color temperature indicates the color temperature of the overlapping illumination.
Therefore, even if the calculated color temperature is the same, the optimum white balance gain (Kr, Kb) differs between non-flash shooting and flash shooting.
[0032]
Therefore, both the non-flash photographing and the flash photographing are prepared for the lookup table.
First, the contents of the look-up table for non-flash photography (white balance gain (Kr, Kb)) are obtained by measuring the optimum values for the external light at each color temperature.
[0033]
Incidentally, Kb (white balance gain to be multiplied by B component) is higher as it is associated with a lower color temperature, and Kr (white balance gain to be multiplied with R component) is higher as it is associated with a higher color temperature. ing.
[0034]
In non-flash photography, since only the outside light illuminates the object scene, the type of the outside light (whether it is a fluorescent lamp) can be determined from the signal for the one image. .
Since the fluorescent lamp has lower color rendering than other external light (non-fluorescent lamp), it is necessary to increase the white balance gain (Kr, Kb) even if the calculated color temperature is the same. For this reason, during non-flash photography, the color temperature calculation unit 15c-2 calculates the color temperature and determines the type of external light (whether it is a fluorescent lamp) based on the same image signal.
[0035]
As the look-up table for non-flash photography of the white balance gain determination unit 15c-3, a fluorescent lamp and a non-fluorescent lamp are prepared separately, and both are selectively used according to the determination result. (See the lower right table in FIG. 2).
On the other hand, the contents of the look-up table for flash photography (white balance gain (Kr, Kb)) are obtained by measuring the optimum values for the flashes of each color temperature (that is, the optimum values for the illumination of the flash alone). It is.
[0036]
Incidentally, in the flash photography look-up table, Kb (white balance gain to be multiplied by B component) is higher as it is associated with a lower color temperature, and Kr (R component is associated with a higher color temperature). The white balance gain to be multiplied is high.
However, since the contents of the look-up table for flash photography (white balance gain (Kr, Kb)) are optimum values for only flash, the specific flash photography scene (the color rendering property of external light is the same as that of flash) It is only suitable for certain flash photography scenes).
[0037]
Therefore, the white balance gain determination unit 15c-3 of the present embodiment devise a reference method (calculated color temperature-reference color temperature curve) of a flash photography lookup table during flash photography. The white balance gain determination unit 15c-3 recognizes whether flash photography or non-flash photography is performed based on a signal from the CPU 15a (the CPU 15a determines the state of the electronic camera body 11 from the state of the operation button 16). It recognizes whether it is flash mode or non-flash mode.)
[0038]
FIG. 3 is a diagram illustrating a look-up table reference method (calculated color temperature-reference color temperature curve) for flash photography by the white balance gain determination unit 15c-3. The horizontal axis is the calculated color temperature, and the vertical axis is the reference color temperature.
First, here, the color temperature of the flash alone illumination is 6500K.
In normal flash photography, the calculated color temperature is often the same as the color temperature (6500K) or otherwise, it is often lower than the color temperature (6500K) due to the influence of external light.
[0039]
In the present embodiment, if the calculated color temperature is higher than the color temperature (6500K) of the flash alone illumination (FIG. 3A), the calculated color temperature is calculated by mistake. Yes, it is considered not to accurately indicate the color temperature of the overlapping illumination of ambient light and flash.
For example, for a flash photography scene with a blue background in the distance, such as a flash photography scene with the sea in the background, the calculated color temperature is higher than the color temperature of the flash alone illumination (6500K) due to the influence of the blue of the sea. It tends to be highly calculated.
[0040]
If the calculated color temperature of this flash photography scene is used as it is as the reference color temperature, a white balance gain (Kr, Kb) that suppresses bluishness is set, so that subjects such as people appear reddish unnaturally. Will be reproduced.
In this case, the white balance gain determination unit 15c-3 of the present embodiment brings the reference color temperature close to the color temperature (6500K) of the illumination with flash alone.
[0041]
For example, the reference color temperature is made to coincide with the color temperature (6500K) of the illumination of the flash alone, regardless of the value of the calculated color temperature.
That is, when the calculated color temperature belongs to the range of FIG. 3A, the calculated color temperature-reference color temperature curve is not “reference color temperature = calculated color temperature” indicated by a thick dotted line, but “reference color temperature = 6500K”. Set to
[0042]
In this way, an image of a flash photography scene with the sea as a background can be reproduced naturally without being unnaturally reddish.
On the other hand, when the calculated color temperature is equal to or lower than the color temperature of the flash alone illumination (6500K) and equal to or higher than the color temperature of illumination equivalent to daylight (here, 5200K) (FIG. 3B). ), The calculated color temperature is considered to be highly reliable, and the calculated color temperature is directly used as the reference color temperature.
[0043]
That is, when the calculated color temperature belongs to the range of FIG. 3B, the calculated color temperature-reference color temperature curve is set to “reference color temperature = calculated color temperature” indicated by a thick dotted line.
Furthermore, in this embodiment, when the calculated color temperature is lower than the color temperature of illumination equivalent to daylight (5200K) (FIG. 3C), the reference color temperature is set to the color temperature of flash only illumination (6500K). ).
[0044]
In particular, when the calculated color temperature is equal to or lower than the color temperature of illumination equivalent to sunset light (here, 3900K) (FIG. 3D), the reference color temperature is the color temperature of the flash alone illumination ( 6500K). For example, the reference color temperature is made to coincide with the color temperature (6500K) of the illumination of the flash alone, regardless of the value of the calculated color temperature.
That is, when the calculated color temperature belongs to the range of FIG. 3D, the calculated color temperature-reference color temperature curve is set to “reference color temperature = 6500K”.
[0045]
This is because flash photography scenes with a red background in the distance are often taken with the aim of the reddishness of the operator, such as when the sunset is the background. At this time, the calculated color temperature is calculated to be 3900K or lower.
If the calculated color temperature of this flash photography scene is used as it is for the reference color temperature, a white balance gain (Kr, Kb) that suppresses redness is set, so that the redness fades and the operator's intention It will be reproduced in a different color.
[0046]
If the reference color temperature is set to the color temperature of flash only illumination (6500K) as in this embodiment, an image as intended by the operator can be obtained.
When the calculated color temperature belongs to a range other than (d) in FIG. 3C, the calculated color temperature-reference color temperature curve is a curve continuous to adjacent straight lines, for example, “reference color temperature = 10400−calculated color”. It is preferable that the temperature is set. In this case, the calculated color temperature-reference color temperature curve as a whole draws a “V-shaped curve”.
[0047]
As described above, in the present embodiment, “the amount of reflection of the calculated color temperature with respect to the white balance gain (Kr, Kb) is positively reduced when the calculated color temperature is within a predetermined range (here, 6500K or more and 5200K or less)”. With this simple process, each flash photography scene is supported.
That is, according to the present embodiment, the white balance gain (Kr, Kb) at the time of flash photography is appropriately set by a relatively simple process.
[0048]
An operation flowchart of the white balance gain determination unit 15c-3 for setting the calculated color temperature-reference color temperature curve to the “V-shaped curve” illustrated in FIG. 3 is, for example, as illustrated in FIG.
That is, first, it is determined which of the four ranges the calculated color temperature belongs to (steps S1, S3, S5).
[0049]
The four ranges are a range of 3900K or less, a range of 3900K to 5200K, a range of 5200K to 6500K, and a range exceeding 6500K.
When the range is 3900K or less or over 6500K (step S1YES or step S1NO → S3NO → S5NO), the reference color temperature is determined to be 6500K (step S2).
[0050]
When the range is from 5200K to 6500K (step S1NO, step S3NO, step S5YES), the calculated color temperature is used as it is for the reference color temperature (step S6).
If it is in the range of 3900K to 5200K (step S1NO, step S3YES), the reference color temperature is determined to be (10400−calculated color temperature) K (step S4).
[0051]
Incidentally, since the interval from the threshold 3900 to the threshold 5200 is equal to the interval from the threshold 5200 to the threshold 6500 in the V-shaped curve shown in FIG. 3, the setting of the slope portion on the left side of the V-shaped (in step S4 in FIG. 4) Operations required for processing are simple (addition / subtraction). The value “10400” is the sum of the threshold 6500 and the threshold 3900.
[0052]
In the white balance gain determination unit 15c-3 of the present embodiment, the reference color temperature range during flash photography is only 3900K to 6500K, so the white balance gain (Kr) prepared in the flash photography lookup table is used. , Kb) may be only an optimum value for 5200K to 6500K (the portion surrounded by a dotted line in the lower right table of FIG. 2).
[0053]
[Supplement to the first embodiment]
In this embodiment, the color temperature of the illumination equivalent to the sunset light is 3900K, but may be replaced with another value of 3000 to 4000K.
Further, since the color temperature of the sunset light varies depending on the region, it is preferable that an optimal value is set according to the region where the electronic camera is used.
[0054]
Further, in this embodiment, the color temperature of the illumination equivalent to daylight is 5200K, but it may be replaced with another value of 5000 to 5500K.
In addition, since the color temperature of daylight varies depending on the region, it is preferable to set an optimal value according to the region where the electronic camera is used.
Further, in this embodiment, the color temperature of the illumination equivalent to the flash is 6500K, but it may be replaced with another value of 6000 to 7000K.
[0055]
Further, since the color temperature of the flash differs depending on the type of electronic flash device 13 and the setting content of the electronic flash device 13, it is preferable to set the color temperature to an optimum value according to the type and setting content.
In the present embodiment, it is preferable that the contents of the flash photography look-up table (white balance gain (Kr, Kb)) also correspond to the type and setting contents of the electronic flash device 13.
[0056]
In the present embodiment, as a lookup table for flash photography, a lookup table in which optimum white balance gains are associated with each color temperature flash is prepared (see FIG. 2). A look has been devised in the reference method (calculated color temperature-reference color temperature curve) (see FIG. 3), in which each calculated color temperature and a white balance gain to be set for each calculated color temperature are associated in advance. Even if an uptable is prepared and the calculated color temperature is used as it is as the reference color temperature, the same effect as described above can be obtained.
[0057]
In addition, the reference method (calculated color temperature-reference color temperature curve) of the flash photography lookup table by the white balance gain determination unit 15c-3 in the present embodiment is not limited to that shown in FIG. It can be modified as shown in FIG. The curves shown in FIG. 5 are given a slight slope so as to rise to the right and to the left in the range (a) and the range (d), respectively.
[0058]
[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIGS.
This embodiment is a modification of the first embodiment. Only differences from the first embodiment will be described.
As shown in FIG. 1, the electronic camera body 11 ′ according to the present embodiment includes a condenser lens 11g and a colorimetric sensor 11h. Based on the output of the colorimetric sensor 11h, the type of external light (whether or not it is a fluorescent lamp) can be identified. In addition, the electronic camera body 11 ′ of this embodiment includes a circuit unit 15 ′ instead of the circuit unit 15.
[0059]
As shown in FIG. 6, the circuit unit 15 ′ according to the present embodiment includes a CPU 15a ′ instead of the CPU 15a in the circuit unit 15 according to the first embodiment, and a white balance control circuit 15c instead of the white balance control circuit 15c. Equal to the one provided with '.
The white balance control circuit 15c ′ is equivalent to the white balance control circuit 15c of the first embodiment provided with a white balance gain determination unit 15c-3 ′ instead of the white balance gain determination unit 15c-3.
[0060]
The CPU 15a ′ of the present embodiment identifies the type of external light (whether it is a fluorescent lamp) based on the output of the colorimetric sensor 11h immediately before flash photography.
Then, the CPU 15a ′ causes the white balance gain determination unit 15c-3 ′ to perform different processes depending on the identification result.
FIG. 7 is a diagram showing a method of referring to a flash photography look-up table (calculated color temperature-reference color temperature curve) by the white balance gain determination unit 15c-3 ′.
[0061]
First, when a non-fluorescent lamp is identified, a reference method similar to that of the first embodiment is employed as shown in FIG. 7I (refer to the first embodiment for details).
On the other hand, when a fluorescent lamp is identified, a reference method as shown in FIG. 7 (II) is adopted. This will be specifically described below.
When the calculated color temperature is equal to or higher than the color temperature of illumination equivalent to daylight (5200K) (FIG. 7 (II) (a) (b)), the calculated color temperature-reference color temperature curve is the first embodiment. Is set the same as
[0062]
On the other hand, when the calculated color temperature is lower than the color temperature of illumination equivalent to daylight (5200K) (FIG. 7 (II) (c)), the reference color temperature is brought close to the color temperature of the illumination (5200K). For example, the reference color temperature is made to coincide with the color temperature (5200K) of the illumination regardless of the value of the calculated color temperature. That is, the calculated color temperature-reference color temperature curve is set to “reference color temperature = 5200K”.
[0063]
This is because a flash photography scene in which the outside light is a fluorescent lamp and the calculated color temperature belongs to this range (FIGS. 7 (II) and (c)) is considered to have a relatively strong influence of the fluorescent lamp. In addition, fluorescent lights that are artificial light unlike natural light such as sunset tend to be disliked by general operators. Therefore, there is a high possibility that the operator desires to remove the fluorescent lamp atmosphere in this flash photography scene as much as possible.
[0064]
However, if the reference color temperature in this range (FIGS. 7 (II) and (c)) matches the color temperature (6500K) of the flash only illumination, the adjacent range (FIGS. 7 (II) and (b)) It becomes discontinuous with the curve (calculated color temperature-reference color temperature curve).
For this reason, the reference color temperature is made equal to the color temperature (5200K) of illumination equivalent to daylight, not the color temperature (6500K) of illumination with flash alone.
[0065]
In this case, the calculated color temperature-reference color temperature curve as a whole draws an “inverse Z-shaped curve”.
An operation flowchart of the white balance gain determination unit 15c-3 ′ for setting the calculated color temperature-reference color temperature curve to the “inverted Z curve” shown in FIG. 7 (II) is as shown in FIG. 8, for example. . In the beginning of FIG. 8, step S21 for determining whether or not the external light is a fluorescent lamp is shown. In the case of a non-fluorescent lamp (step S21 NO), the operation shown in FIG. 4 of the first embodiment is executed.
[0066]
If it is a fluorescent lamp, it is first determined which of the three ranges the calculated color temperature belongs to (steps S3 and S5).
The three ranges are a range below 5200K, a range from 5200K to 6500K, and a range above 6500K.
When it is in the range exceeding 6500K (step S3NO → S5NO), the reference color temperature is determined to be 6500K (step S2).
[0067]
When the range is from 5200K to 6500K (step S3NO, step S5YES), the calculated color temperature is used as it is for the reference color temperature (step S6).
If it is in the range below 5200K (step S3 YES), the reference color temperature is determined to be 5200K (step S24).
As described above, in the present embodiment, in the first embodiment, the type of external light (whether it is a fluorescent lamp) is further identified from the output of the colorimetric sensor 11h, and the calculated color temperature is determined according to the identified type. The relationship between the range and the reflection amount is variable.
[0068]
Then, whether it is a fluorescent lamp or a non-fluorescent lamp, “when the calculated color temperature is within a predetermined range, the amount of reflection of the calculated color temperature with respect to the white balance gain (Kr, Kb) is actively reduced”. It corresponds to each of various flash photography scenes by simple processing.
Therefore, also in the present embodiment, the white balance gain (Kr, Kb) at the time of flash photography is appropriately set by a relatively simple process.
[0069]
[Supplement of the second embodiment]
In the present embodiment, the colorimetric sensor 11h that receives light that has passed through the photographing lens 12 is used as the colorimetric sensor. However, instead of such a colorimetric sensor, the front part of the electronic camera body 11 or the like is used. It is also possible to use an external light sensor that receives light that does not pass through the photographing lens 12 from the direction of the object field.
[0070]
Alternatively, the electronic camera body 11 may perform non-flash shooting immediately before flash shooting, and the type of external light may be obtained based on the image acquired thereby.
In the present embodiment, a lookup table in which an optimum white balance gain is associated with each color temperature flash is prepared as a lookup table for flash photography (see FIG. 6). The reference method (calculated color temperature-reference color temperature curve) has been devised (see 7 (I) and (II)) to calculate each calculated color temperature and the white balance gain to be set for each calculated color temperature. Even if a lookup table associated in advance is prepared and the calculated color temperature is directly used as the reference color temperature, the same effect as described above can be obtained.
[0071]
However, in the present embodiment, the set white balance gain is different between when the external light at the time of flash photography is a fluorescent lamp and when it is a non-fluorescent lamp. Need to provide two types of fluorescent lamps and non-fluorescent lamps (at least in the range where the calculated color temperature is below 5200).
[Others]
Note that the white balance control circuit (15c, 15c ′) of each of the above embodiments is either when the calculated color temperature belongs to the range (a) shown in FIG. 3 (FIG. 7) or when the calculated color temperature belongs to the range (c). In this case, the reflected amount of the calculated color temperature with respect to the white balance control value (white balance gain) is reduced, but it is configured to be reduced only when belonging to the range (a), or only when belonging to the range (b). It can also be configured to reduce.
[0072]
In each of the above embodiments, a look-up table is used for setting the white balance control value (white balance gain), but it goes without saying that other methods may be applied for the setting.
[0073]
【The invention's effect】
As described above, according to the present invention, an electronic camera and a white balance control circuit that can appropriately set a white balance control value at the time of flash photography by a relatively simple process are realized.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a camera system according to a first embodiment and a second embodiment.
2 is a block diagram of a circuit unit 15 provided in the electronic camera body 11. FIG.
FIG. 3 is a diagram showing a look-up table reference method (calculated color temperature-reference color temperature curve) for flash photography by the white balance gain determination unit 15c-3.
FIG. 4 is an operation flowchart (part) of a white balance gain determination unit 15c-3.
FIG. 5 is a diagram showing another example of a method for referring to a flash photography lookup table (calculated color temperature-reference color temperature curve) by the white balance gain determination unit 15c-3.
FIG. 6 is a block diagram of a circuit unit 15 ′.
FIG. 7 is a diagram showing a look-up table reference method (calculated color temperature-reference color temperature curve) for flash photography by the white balance gain determination unit 15c-3 ′.
FIG. 8 is an operation flowchart (part) of a white balance gain determination unit 15c-3 ′.
[Explanation of symbols]
11 Electronic camera body
12 Shooting lens
11a mirror
11b screen
11c Penta prism
11d eyepiece
11h Colorimetric sensor
11g condenser lens
11e Shutter
11f CCD image sensor
13 Electronic flash device
15,15 'circuit part
16 Operation buttons
15a, 15a 'CPU
15b Signal processing circuit
15c, 15c 'White balance control circuit
15c-1 White balance processing section
15c-2 Color temperature calculator
15c-3, 15c-3 ′ White balance gain determination unit
15d color conversion circuit
15e gradation conversion circuit
15f image memory

Claims (16)

In an electronic camera equipped with a flash light emitting device or a connection terminal to the flash light emitting device,
Imaging means for imaging the outside world and acquiring image data;
Based on the image data acquired during flash emission by the flash light emitting device, color temperature calculation means for calculating the color temperature of overlapped illumination by external light and flash light;
White balance control value determining means for determining a white balance control value for the image data in accordance with the calculated color temperature that is the calculated color temperature;
The white balance control value determining means includes
When the calculated color temperature falls within a predetermined range, an amount of reflection of the calculated color temperature with respect to the white balance control value is reduced. The electronic camera according to claim 1,
The white balance control value determining means includes
An electronic camera characterized in that when the calculated color temperature is higher than the color temperature of the flash alone illumination, the white balance control value is brought close to an optimum value for the illumination. The electronic camera according to claim 2,
The white balance control value determining means includes
When the calculated color temperature is higher than the color temperature of the flash alone illumination, the white balance control value is made to coincide with the optimum value for the illumination. In the electronic camera according to any one of claims 1 to 3,
The white balance control value determining means includes
An electronic camera characterized in that when the calculated color temperature is lower than the color temperature of illumination equivalent to daylight, the white balance control value is brought close to an optimum value for illumination of the flash alone. The electronic camera according to claim 4,
The white balance control value determining means includes
An electronic camera characterized in that when the calculated color temperature is lower than the color temperature of illumination equivalent to daylight and lower than the color temperature of illumination equivalent to sunset light, the white balance control value is made closer to the optimum value. The electronic camera according to claim 5,
The white balance control value determining means includes
An electronic camera characterized in that when the calculated color temperature is lower than the color temperature of illumination equivalent to daylight and lower than the color temperature of illumination equivalent to sunset light, the white balance control value is matched with the optimum value. In the electronic camera according to any one of claims 1 to 3,
The white balance control value determining means includes
The electronic camera according to claim 1, wherein when the calculated color temperature is lower than a color temperature of illumination equivalent to daylight, the white balance control value is brought close to an optimum value for the illumination. The electronic camera according to claim 1,
Means for identifying the type of external light during non-emission of the flashlight;
The white balance control value determining means includes
An electronic camera, wherein the relationship between the calculated color temperature range and the reflection amount is varied according to the identified type. A white balance control circuit applied to an electronic camera capable of flash photography,
Based on image data acquired by flash photography with the electronic camera, color temperature calculation means for calculating the color temperature of overlapping illumination with external light and flash,
White balance control value determining means for determining a white balance control value for the image data in accordance with the calculated color temperature that is the calculated color temperature;
The white balance control value determining means includes
When the calculated color temperature belongs to a predetermined range, a reflection amount of the calculated color temperature with respect to the white balance control value is reduced. In the white balance control circuit according to claim 9,
The white balance control value determining means includes
When the calculated color temperature is higher than the color temperature of the flash alone illumination, the white balance control circuit approaches the optimum value for the illumination. The white balance control circuit according to claim 10,
The white balance control value determining means includes
When the calculated color temperature is higher than the color temperature of the flash alone illumination, the white balance control circuit makes the white balance control value coincide with the optimum value for the illumination. In the white balance control circuit according to any one of claims 9 to 11,
The white balance control value determining means includes
A white balance control circuit, wherein when the calculated color temperature is lower than a color temperature of illumination equivalent to daylight, the white balance control value is brought close to an optimum value for illumination of the flash alone. The white balance control circuit according to claim 12,
The white balance control value determining means includes
When the calculated color temperature is lower than the color temperature of illumination equivalent to daylight and lower than the color temperature of illumination equivalent to sunset light, the white balance control value is made closer to the optimum value. circuit. The white balance control circuit according to claim 13, wherein the white balance control value determining means includes:
When the calculated color temperature is lower than the color temperature of illumination equivalent to daylight and lower than the color temperature of illumination equivalent to sunset light, the white balance control value is made to coincide with the optimum value. circuit. The electronic camera according to any one of claims 9 to 11,
The white balance control value determining means includes
When the calculated color temperature is lower than the color temperature of illumination equivalent to daylight, the white balance control circuit approaches the optimum value for the illumination. In the white balance control circuit according to claim 9,
The electronic camera is
An electronic camera capable of identifying the type of external light;
The white balance control value determining means includes
A white balance control circuit, wherein the relationship between the calculated color temperature range and the reflection amount is varied according to the identified type.

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